We’re getting more details on who will be stepping in as Good Morning America guest hosts while Robin Roberts is on medical leave. Stephen Colbert, the cast of Modern Family and Rob Lowe will be coming up soon, the Associated Press reports. The show’s senior executive producer Tom Cibrowski says a different cast member of Modern Family will be featured each day for a week as the new television season begins. As GMA did with Jessica Simpson last week, celebrities will be featured during the second hour alongside show regulars George Stephanopoulos, Josh Elliott, Lara Spencer and Amy Robach. “It shows them in a different light for a little bit and you get to see them do something different,” Cibrowski said. “It might be a little funny if they have to read the prompter and there’s some slip-up. It’s all spontaneous.” Roberts went on medical leave on August 30 for treatment of MDS, a blood and bone marrow disease. She’s due to undergo a bone marrow transplant this week.